Methods and apparatus for determining and/or communicating parameter switching point information in wireless communications systems including wireless terminals supporting multiple wireless connections

ABSTRACT

Methods and apparatus for indicating parameter change points with respect to multiple connections (wireless links) by transmitting a single message, e.g., over one of the connections, is described. A base station corresponding to at least one connection, considers the approximate timing relationship between the connections, selects one of the connections, selects an intended parameter switching point for that connection, determines a symbol time offset from the selected switching point such that the other intended switching points of other wireless links can be unambiguously interpreted by the wireless terminal from information indicating the offset with respect to the selected link, and communicates information indicating the offset and the wireless link to which said offset applies. A wireless terminal receives the information, identifies a time referenced with respect the timing structure of the identified wireless link and then determines individual parameter switching points for the other wireless links.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application Ser. No. 11/314,721filed on Dec. 21, 2005 for “Methods and Apparatus for Determining and/orCommunicating Parameter Switching Point Information in WirelessCommunications Systems Including Wireless Terminals Supporting MultipleWireless Connections” which is hereby incorporated in its entirety byreference.

FIELD OF THE INVENTION

The present invention relates to communications systems and, moreparticularly, to methods and apparatus for determining and/orcommunicating parameter switching point information, e.g., in a wirelesscommunications network including wireless terminals supporting multipleconcurrent wireless links.

BACKGROUND

In wireless communications systems there are typically controlparameters which need to be changed during operations. Some of theseparameters are used in defining connections and logical link layeroperations. One such type of parameter is a key, e.g. an encryption key.In wireless communications systems in which a wireless terminal supportsonly a single concurrent connection and parameter switching points arelimited to predetermined points in a recurring timing structure, aparameter change message can be sent which unambiguously communicateswhen to perform the parameter switch, e.g., the messages identifies asuperslot boundary in a repetitive timing structure being used by thebase station attachment point.

If a system allows for a wireless terminal to maintain multiple wirelesscommunications links at the same time, which may not be synchronized intime at the wireless terminal and/or basestation(s), signaling when aparameter is to be changed with individual ones of the wirelesscommunications links is much more complicated than in the case ofsignaling with respect to a parameter change point which is to beimplemented for a single wireless connection.

To facilitate the implementation of systems where a wireless terminalmight support multiple wireless communications links at the same time,there is a need for new methods and apparatus which provide forsignaling parameter switching points corresponding to multipleconnections using the same parameter which needs to be switched. Methodsand apparatus which facilitate more efficient signaling techniquesconserving air link resources would be beneficial. Methods and apparatuswhich provide, for each of multiple connections, for an unambiguousunderstanding by the base station attachment point and the wirelessterminal, as to a parameter switching point with respect to therepetitive timing structure implemented for that connection would bebeneficial.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a drawing of an exemplary communications system implemented inaccordance with the present invention.

FIG. 2 is a drawing of an exemplary base station implemented inaccordance with the present invention and using methods of the presentinvention.

FIG. 3 is a drawing of an exemplary wireless terminal, e.g., mobilenode, implemented in accordance with the present invention and usingmethods of the present invention.

FIG. 4 is a drawing of a portion of an exemplary wireless communicationssystem implemented in accordance with the present invention and usingmethods of the present invention, used to illustrate various features ofthe present invention.

FIG. 5 is a drawing illustrating exemplary parameter switching inaccordance with the present invention.

FIG. 6 is another drawing illustrating exemplary parameter switching inaccordance with the present invention.

FIG. 7 is a drawing of an exemplary wireless communications systemimplemented in accordance with the present invention and using methodsof the present invention.

FIG. 8 is a drawing illustrating exemplary parameter switching inaccordance with the present invention.

FIG. 9 is a flowchart of an exemplary method of operating a base stationin accordance with the present invention.

FIG. 10 is a flowchart of an exemplary method of operating a wirelessterminal to receive and process parameter switching point information inaccordance with the present invention.

SUMMARY OF THE INVENTION

The present invention is directed to methods and apparatus fordetermining parameter switching points and/or communicating parameterswitching point information. The methods and apparatus of the inventionare particular well suited for systems where wireless terminals cansupport multiple concurrent wireless communications links. The wirelesscommunications links may or may not be timing synchronized. In fact,even if timing synchronization exists at a base station with respect tomultiple communications links, timing synchronization may not exist atthe wireless terminal for the communications links due to differenttransmission distances between the wireless terminal and the variousdifferent physical attachment points to which the communications linkscorrespond.

A wireless communications link, also sometimes referred to a wirelesslink, refers to a connection. The connection may be between, forexample, a wireless terminal and a base station physical attachmentpoint. A wireless link is normally implemented as an airlink connection.The base station physical attachment point to which a wireless linkcorresponds, may be identified, at least locally, by one or acombination of physical layer identifiers. Such physical layeridentifiers may include, for example, a cell identifier, a sector orsector type identifier, and/or a carrier or tone block identifier. Insome but not all embodiments, a combination of a cell identifier, sectortype identifier and carrier or tone block identifier is used to identitya physical attachment point. The physical layer identifier orcombination of physical layer identifiers which may be used in a systemto identify a physical attachment point can vary depending on the systemimplementation, e.g., if multiple sectors and/or carriers per sector aresupported.

It should be appreciated that multiple wireless links may correspond tothe same link layer link. For example, different sectors of a basestation implemented using a single link layer controller may havephysical attachment points of different sectors corresponding to thesame link layer link. Similarly, when a sector supports multiplecarriers or tone blocks, each corresponding to a different physicalattachment point from a physical layer perspective, the physicalattachment points corresponding to different carriers or tone blocksmay, but do not necessarily have to, operate under the same link layercontroller. Thus multiple physical layer attachment points maycorrespond to the same link layer link. While multiple physicalattachment points may correspond to a single link layer link, normallymultiple link layer links used concurrently by the same wirelessterminal do not correspond to the same physical attachment point.

The possibility that timing synchronization does not exist for multipleconcurrent wireless links, even when they correspond to the same linklayer link or base station, complicates the issue of communicating whena parameter used for processing information communicated over thecurrent links should be changed with respect to individual wirelesslinks in the plurality of concurrent links. The issue may beencountered, e.g., when an encryption parameter used for multiplewireless links (connections) corresponding to different physicalattachment points but the same logical link, is to be changed. As notedabove, the multiple different concurrent connections may, but often arenot, fully synchronized with one another. When they are not fullysynchronized, the implementation of the parameter change will often bedifferent on the different links due to the lack of full timingsynchronization.

In a wireless communications system, where a wireless terminal supportsmultiple simultaneous wireless communications connections with aplurality of different base station sector attachment points,unambiguously communicating parameter switching information such thatboth the base station(s) and the wireless terminal have the sameunderstanding as to which parameter (old or new) to use at any giventime with respect to the timing structure being used corresponding toeach wireless link can be problematic. For example, consider that thesame parameter may be used with respect to communications over multipleconnections and may need to be switched. Consider that different basestation sector attachment points may not be synchronized. In additionconsider that different base stations may be timing independent of oneanother such that the timing structure with respect to one base stationdrifts with respect to the timing structure with respect to another basestation. In addition a wireless terminal's location with respect todifferent base station sector attachment points influencessynchronization with respect to each of the base station sectorattachment points, e.g., due to the differences of signal path delay.Under such conditions, a wireless terminal's view of the timing offsetsbetween different base station sector attachment points may be differentthan a base station's understanding.

In such a case, using a single parameter change message sent from a basestation identifying a parameter switching point as a superslot boundarywith respect to a first connection may be ambiguous with respect to theother connections. However, sending multiple parameter switchingmessages, e.g., one for each connection is inefficient in terms of theuse of air link resources. In addition, if some of the multipleparameter switching messages are successfully received while other arenot, this can create problems in the switching operation, e.g.,especially if time sensitive user data is being partitioned among theplurality of connections.

Various embodiments of the present invention are directed to methods andapparatus for using a single message to communicate sufficientinformation to a wireless terminal so that a wireless terminal candetermine the appropriate time to change a parameter being used withrespect to a plurality of wireless links maintained by the wirelessterminal at the same time. The single message may identify the parameterto be changed or the parameter to which the message applies may beknown, e.g., from the time the message is transmitted or some otherinformation.

Some embodiments of the invention are directed to operating a basestation to indicate to a wireless terminal a plurality of parameterswitching points, different ones of said parameter switching pointscorresponding to different wireless communications links. The wirelesscommunications links in various embodiments have a repetitive timingstructure, e.g., an uplink and/or downlink timing structure. Theindicated switching points correspond to positions, e.g., superslot,within the repetitive timing structure of a corresponding one of thedifferent communication links where parameter switching may beimplemented.

In one particular exemplary embodiment, the method, from a base stationperspective, includes selecting an offset point in time with respect toa first link in a plurality of concurrent communications links with awireless terminal, the selected offset point in time being offset intime from the parameter switching point of the first link by a timeoffset. The base station then transmits information indicating theoffset point in time to the wireless terminal for use by the wirelessterminal in determining the parameter switching points correspondingsaid plurality of concurrent communications links. The switching pointin time that is determined, e.g., on a per link basis, for differentlinks, may be different due to differences in wireless linksynchronization and/or the repetitive timing structure used on thedifferent wireless links.

Various features of the present invention are directed to methods andapparatus for operating a wireless terminal to receive and processparameter switching point information and to determine from theinformation received in a message the appropriate time to change theparameter with respect to a plurality of different wireless links. Themethod of operating a wireless terminal in some embodiments includesreceiving parameter switching point information over at least one of aplurality of wireless communications links corresponding to the wirelessterminal where the received switching point information indicates apoint offset from a parameter switching point to be used for a first oneof the wireless links. The wireless terminal determines a referencepoint in time from the received parameter switching point informationcorresponding to the first wireless communications link, said firstwireless communications link being one of said plurality of wirelesscommunications links. In addition, from the received information, thewireless terminal proceeds to determine a plurality of individualparameter switching points, each determined individual parameterswitching point corresponding to a different one of said plurality ofwireless communications links. Information about timing synchronizationdifferences between the different wireless links relative to the firstlink may be used in making the determination as to when the switchingpoint of links other than the first link is to be implemented.Differences, if any, in terms of the repetitive timing structure andlocation of permissible switching points with respect to different linksmay also be taken into consideration and used by the wireless terminalin determining the parameter switching point to be used for the variousindividual wireless links.

An exemplary embodiment of the present invention shall now be described.Other embodiments are also possible. In the exemplary embodiment awireless terminal has multiple concurrent connections with a pluralityof base station attachment points, each base station attachment pointcorresponding to a base station cell, a sector and a downlink toneblock. Each connection is associated with a timing structure includingpotential parameter switching points within the structure, e.g.,superslot boundaries. From the wireless terminal's perspective thetiming structures corresponding to the multiple concurrent connectionsare not necessarily synchronized, e.g., due to lack of synchronizationwith respect to the base station sector transmitters, due to receiverprocessing delay differences and/or due to path delay differences. Aparameter, e.g., an encryption key, used for communications over aplurality of the concurrent wireless links is to be switched. Forexample, the encryption key, in some embodiments is used for multipleconnections for the same wireless terminal corresponding to the samelogical link. For example in some embodiments at some times, packets ofuser data to be communicated are partitioned and/or communicated withsome degree of redundancy among a plurality of connections. A basestation corresponding to one of the sector attachment points, considersthe approximate timing relationship between the connections, selects oneof the wireless links, selects an intended parameter switching point forthat wireless link at a superslot boundary, determines a symbol timeoffset from the selected superslot boundary such that the other intendedswitching points of other wireless links should be unambiguouslyinterpreted by the wireless terminal, and communicates parameterswitching point information. In some embodiments, the parameterswitching point information includes: a connection identifier, asuperslot identifier, and a symbol time offset. In some embodiments, theconnection identifier is not communicated with the wireless terminalrecognizing that the wireless link over which the parameter switchingpoint information was communicated is the connection to which thecommunicated timing information is being referenced. A wireless terminalreceives the communicated switching point parameter information, whichidentifies a time referenced with respect to the timing structure of theidentified connection. The wireless terminal identifies, forconnections, e.g., each connection in the plurality of connections, aparameter switching point using a predetermined agreed upon relationshipof the intended switching point to the time reference. A function, e.g.,predetermined or preprogrammed function known to the wireless terminaland base station, may be used to implemented the predetermined agreedupon relationship. In some embodiments, the parameter switching point isthe last preceding superslot boundary prior to the identified referencedtime. For each connection, the wireless terminal implements theparameter switching using the determined parameter switching point timecorresponding to the connection and parameter switching protocol rules.While various embodiments have been discussed in the summary above, itshould be appreciated that not necessarily all embodiments include thesame features and some of the features described above are not necessarybut can be desirable in some embodiments. Numerous additional features,embodiments and benefits of the present invention are discussed in thedetailed description which follows.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows an exemplary communication system 100 implemented inaccordance with the present invention including multiple cells: cell 1102, cell M 104. Exemplary system 100 is, e.g., an exemplary OFDM spreadspectrum wireless communications system such as a multiple access OFDMsystem. Each cell (102, 104) of exemplary system 100 includes threesectors. Cells which have not been subdivided into multiple sectors(N=1), cells with two sectors (N=2) and cells with more than 3 sectors(N>3) are also possible in accordance with the invention. Each sectorsupports one or more carriers and/or downlink tones blocks. In someembodiments at least some of the sectors support three downlink tonesblocks. In some embodiments, for each downlink tone block there is acorresponding uplink tone block. Cell 102 includes a first sector,sector 1 110, a second sector, sector 2 112, and a third sector, sector3 114. Similarly, cell M 104 includes a first sector, sector 1 122, asecond sector, sector 2 124, and a third sector, sector 3 126. Cell 1102 includes a base station (BS), base station 1 106, and a plurality ofwireless terminals (WTs) in each sector 110, 112, 114. Sector 1 110includes WT(1) 136 and WT(N) 138 coupled to BS 106 via wireless links140, 142, respectively; sector 2 112 includes WT(1′) 144 and WT(N′) 146coupled to BS 106 via wireless links 148, 150, respectively; sector 3114 includes WT(1″) 152 and WT(N″) 154 coupled to BS 106 via wirelesslinks 156, 158, respectively. Similarly, cell M 104 includes basestation M 108, and a plurality of wireless terminals (WTs) in eachsector 122, 124, 126. Sector 1122 includes WT(1″″) 168 and WT(N″″) 170coupled to BS M 108 via wireless links 180, 182, respectively; sector2124 includes WT(1″″′) 172 and WT(NIII″) 174 coupled to BS M 108 viawireless links 184, 186, respectively; sector 3 126 includes WT(1″″″)176 and WT(N″″″) 178 coupled to BS M 108 via wireless links 188, 190,respectively.

System 100 also includes a network node 160 which is coupled to BS1 106and BS M 108 via network links 162, 164, respectively. Network node 160is also coupled to other network nodes, e.g., other base stations, AAAserver nodes, intermediate nodes, routers, etc. and the Internet vianetwork link 166. Network links 162, 164, 166 may be e.g., fiber opticcables. Each wireless terminal, e.g. WT 1 136, includes a transmitter aswell as a receiver. At least some of the wireless terminals, e.g., WT(1)136, are mobile nodes which may move through system 100 and maycommunicate via wireless links with the base station in the cell inwhich the WT is currently located, e.g., using a base station sectorattachment point. The wireless terminals, (WTs), e.g. WT(1) 136, maycommunicate with peer nodes, e.g., other WTs in system 100 or outsidesystem 100 via a base station, e.g. BS 106, and/or network node 160.WTs, e.g., WT(1) 136 may be mobile communications devices such as cellphones, personal data assistants with wireless modems, etc.

The wireless terminals (136, 138, 144, 146, 152, 154, 168, 170, 172,174, 176, 178) support multiple simultaneous connections with differentbase station sector attachment points. Exemplary wireless terminal (N″″)170, situated in a cell M sector boundary area and has one wirelesscommunications link 182 with a base station M sector 1 attachment pointand another wireless communications link 183 with a base station Msector 2 attachment point. Exemplary WT (N″) 146, situated in a cellboundary area between cell 1 102 and cell M 104 has one wirelesscommunications link 150 with a base station 1 sector 2 attachment pointand another wireless communications link 151 with a base station Msector 3 attachment point. Exemplary WT(1) 136, situated in cell 1sector 1 has one wireless communications link 140 with a base station 1sector 1 attachment point and another wireless communications link 141with a different base station 1 sector 1 attachment point. Each basestation sector attachment point corresponds to a base station cell, asector, and a downlink tone block.

In some embodiments, synchronization exists with respect to some basestation sector attachment points with respect to one another, while somebase station sector attachment points are asynchronous with respect toone another. For example in some embodiments, with respect to twodifferent downlink tone blocks corresponding to the same base stationsector there is precise synchronization at the base station; withrespect to different adjacent sectors of the same base station there isa high level of synchronization, e.g. to within a symbol transmissiontime period. In some such embodiments, two sector base stationtransmitters of the same base station are synchronized to within amicro-second. Continuing with the example, base station sectortransmitters of different base stations are asynchronous.

In some embodiments, the base station sector transmitters of the samecell are asynchronous. In some embodiments, the downlink timingstructure corresponding to different base station sector attachmentspoints of the same sector of the same cell, but using different downlinktone blocks are synchronous at the base station. In some embodiments,the downlink timing structure corresponding to different base stationsector attachments points of the same sector of the same cell, but usingdifferent downlink tone blocks are asynchronous at the base station.

In accordance with the present invention, a base station (106, 108)determines parameter switching points for one or more wirelesscommunications links, e.g., pertaining to switching a parameter such asan encryption key, corresponding to a wireless terminal, e.g., WT 170 orWT 151, or WT 136, and communicates switching point information to thewireless terminal, the switching point information including an offsetincluding a symbol time index referenced with respect to one of thewireless communications links. The wireless terminal receives andprocesses the switching point information, and determines switchingpoints corresponding to each of one or more wireless communicationslinks, each wireless communications link representing a connectionbetween a base station sector attachment point and the wirelessterminal. In some embodiments, the parameter being switched correspondsto a parameter used for multiple physical connections corresponding tothe same logical link.

In some embodiments, a wireless terminal has a plurality of concurrentwireless connections including a first subset of connectionscorresponding to a first logical link and a second subset of connectionscorresponding to a second logical link, said first subset and saidsecond subset being non-overlapping and said first and second logicallinks being different. In such an embodiment, a parameter to be switchedmay be a parameter that corresponds to the first logical link and thefirst subset of connections, but not to the second logical link andsecond subset of connections. In some such embodiments, the parameterswitching methods in accordance with the present invention performed bythe base station and wireless terminal, under such conditions, considertiming related to the timing structures of the first subset ofconnections, but not to the second subset of connections.

FIG. 2 is a drawing of an exemplary base station 200 implemented inaccordance with the present invention and using methods of the presentinvention. Exemplary base station 200 may be any of the exemplary basestations (106, 108) of FIG. 1, 402 of FIG. 4, or (702, 724) of FIG. 7.Exemplary base station 200 includes one or more sector receiver modules(sector 1 receiver module 202, . . . , sector N receiver module 204),one or more sector transmission modules (sector 1 transmission module206, . . . , sector N transmission module 208), a processor 210, I/Ointerface 212 and memory 214 coupled together via bus 216 over which thevarious elements interchange data and information.

Sector 1 receiver module 202, e.g., an OFDM sector receiver, is coupledto sector 1 receive antenna 203 via which the base station receivesuplink signals from wireless terminals directed to a sector 1 attachmentpoint of the base station. Sector 1 receiver module 202 includes adecoder 218 used for decoding at least some of the received uplinksignals. Sector N receiver module 204, e.g., an OFDM sector receiver, iscoupled to sector N receive antenna 205 via which the base stationreceives uplink signals from wireless terminals directed to a sector Nattachment point of the base station. Sector N receiver module 204includes a decoder 220 used for decoding at least some of the receiveduplink signals.

Sector 1 transmission module 206, e.g., an OFDM sector transmitter, iscoupled to a sector 1 transmit antenna 207 via which the transmissionmodule transmits downlink signals to wireless terminals. Sector 1transmission module 206 includes an encoder 222 which is used to encodeat least some downlink data/information prior to transmission. Sector Ntransmission module 208, e.g., an OFDM sector transmitter, is coupled toa sector N transmit antenna 209 via which the transmission moduletransmits downlink signals to wireless terminals. Sector N transmissionmodule 208 includes an encoder 224 which is used to encode at least somedownlink data/information prior to transmission. The transmissionmodules (206, 208) are used for transmitting information indicating anoffset point in time to a wireless terminal, e.g., as part of aparameter switching message, to indicate to the wireless terminal aplurality of parameter switching points, different ones of the parameterswitching points corresponding to different wireless communicationslinks, e.g., different simultaneous wireless communications linksbetween the wireless terminal and base station attachment points.

I/O interface 212 couples base station 200 to the Internet and/or othernetwork nodes, e.g., other base stations, routers, AAA nodes, home agentnodes, etc. I/O interface 212 provides an interface to a backhaulnetwork, thus allowing a wireless terminal using a base station 200attachment point to participate in a communications session with anotherwireless terminal using a different base station as its point of networkattachment. Timing information, e.g., coarse timing information,pertaining to other base stations, e.g., adjacent base stations is, insome embodiments, communicated via I/O interface 212. In this way, basestation 200 is able to use this timing information, when making adecision regarding parameter switching offset timing in a case where awireless terminal is connected to both base station 200 and an adjacentbase station, and the parameter to be switched is to be switched withrespect to wireless connections corresponding to both BS 200 and theadjacent base station.

Memory 200 includes routines 226 and data/information 228. The processor210, e.g., a CPU, executes the routines 226 and uses thedata/information 228 in memory 214 to control the operation of the basestation 200 and implement the methods of the present invention.

Routines 226 include a communications routine 230 and base stationcontrol routines 232. The communications routine 230 implements thecommunications protocols used by the base station 200. Base stationcontrol routines 232 include a scheduler module 234, an offset pointselection module 236, a parameter switching message generation module238, and a transmission control module 240.

Scheduler module 234, e.g., a scheduler, schedules a plurality ofwireless terminal users. The scheduler module assigns uplink anddownlink segments to the wireless terminals. For example, for eachattachment point of the base station corresponding to a sector and toneblock, the base station scheduler partitions the available air linkresources between a plurality of wireless terminals currently using thatattachment point.

Offset point selection module 236 selects an offset point in time withrespect to a first link in a plurality of wireless communications linkswhich is offset in time from a parameter switching point correspondingto the first link by a time offset, the time offset being selected foruse in indicating a plurality of switching points, each switching pointcorresponding to a position within the repetitive timing structure of acorresponding one of the different communications links. Selectionmodule 236 selects an offset point in time with respect to a first linkby selecting a time which occurs in the timing structure of the firstlink which is offset from the parameter switching point corresponding tothe first link by at least one symbol time period. In addition,selection module 236 perform its selection such that the switching pointin time for each of the additional wireless links in the plurality ofwireless links corresponding to the wireless terminal are also offset intime by at least one symbol time period.

Parameter switching point message generation module 238 generates aparameter switching message including a timing offset with respect to afirst link which is at least one symbol time period from a switchingboundary. For example, in one exemplary embodiment, the generatedparameter switching message includes a superslot identifier, a symboltime identifier and a link identifier. In some embodiments, the linkidentifier is a connection identifier including a cell identifier, asector type identifier, and a tone block identifier. In some suchembodiments, the connection identifier is unique locally in the systemsuch that a wireless terminal having multiple simultaneous connectionswill have unique connection identifiers corresponding to eachconnection. In some embodiments, the generated parameter switchingmessage includes a superslot identifier and a symbol time identifier,but does not include a link identifier. In some embodiments, theparameter switching message is a portion of a larger message.

Transmission control module 240 controls the operation of sectortransmitter modules (206, 208). The transmission control module 240, insome embodiments, controls a sector transmission module (206,208) totransmit to the wireless terminal information indicating which one ofsaid communications links said offset point in time corresponds to,e.g., a parameter switching message including a time offset and linkidentification information, e.g., a connection identifier. In someembodiments, the transmission control module 240 controls the basestation to use the sector transmitter module corresponding to the firstlink to which the offset point in time is being specified to be the linkwhich communicates the parameter switching information to the wirelessterminal. In this way, the base station is able to communicate theidentity of the first link among a plurality of links withouttransmitting express information identifying which one of a plurality oflinks the offset point in time corresponds to.

In some embodiments, a transmission module, e.g., sector 1 transmissionmodule 206, transmits information indicating the selected offset pointin time at a point in time prior to the selected offset point in time,which precedes the switching point corresponding to the first link, byat least 5 times the period between potential switching points in therepetitive timing structure being used for the first link. For example,in some embodiments, potential switching points correspond to superslotboundaries, and the information is transmitted initially at a point intime at least 5 superslots prior to the indicated switching point. Thisintentional early initial transmission allows for the possibility ofretransmission in the event that the message is not successfullyrecovered by the wireless terminal. In some such embodiments, atransmission module, e.g., sector transmission module 206, transmitsindicating the selected offset point in time at a point in time prior tothe selected offset point in time which precedes each switching pointcorresponding to different ones of a plurality of wireless links beingmaintained with the wireless terminal by at least 5 times the periodbetween potential switching points. In some embodiments, differentwireless communications links use different timing structure and/ordifferent periods between potential switching points, and for a givenwireless link, the communicated switching point information istransmitted at a point in time prior to the switching point by at leastfive times the period between potential switching points.

In some embodiments, a transmission module, e.g., sector 1 transmissionmodule 206, transmits information indicating the selected offset pointin time at a point in time prior to the selected offset point in time,which precedes the switching point corresponding to the first link, byat least 40 times the period between potential switching points in therepetitive timing structure being used for the first link, e.g., 40superslots. In some embodiments, the transmitted information indicates aselected switching point for the first link at last 40 superslots intothe future and at most 143 superslots into the future.

Data/information 228 includes system data/information 242 and wirelessterminal data/information 244. System data/information 242 includes oneor more base station sector sets of information corresponding to thesectors of the base station (base station 25 sector 1 information 245, .. . base station sector N information 246) and switching protocolinformation 248. Base station sector 1 information 245 includes one ormore of sets of attachment point information (attachment point 1information 250, . . . , attachment point N information), each set ofattachment point information corresponding to a different downlink toneblock used by the base station sector. In some embodiments, eachdownlink tone block has a corresponding uplink tone block. Attachmentpoint 1 information includes identification information 254 andtiming/frequency structure information 256. Identification information254 includes base station cell, sector, tone block and/or carrieridentification information. In some embodiments at least some of thebase station identification information is communicated via downlinkbroadcast signals such as beacon and/or pilot signals. Timing/frequencystructure information 256 includes downlink and uplink timing andfrequency structure information. In some embodiments, for a givenattachment point, there is a downlink tone block, a downlink channelstructure, downlink tone hopping sequencing, and a downlink timingstructure following a repetitive pattern; in addition there is an uplinktone block, an uplink channel structure, uplink tone hopping sequencing,and an uplink timing structure following a repetitive pattern. In somesuch embodiments, for a given attachment point the uplink and downlinktiming structures are coupled together, e.g., via a fixed timing offsetat the base station. Timing frequency structure information 256 includessuperslot boundary information 258. In various embodiments, potentialparameter switching points for a communications link are limited tooccur at pre-selected timing boundaries being used by a communicationslink. In some embodiments, the pre-selected timing boundaries occur atfixed time spacing. In some embodiments the pre-selected timingboundaries are superslot boundaries which are spaced apart by at least101 OFDM symbol transmission time periods, e.g., 114 OFDM symboltransmission time periods.

The downlink timing structure for a given attachment point, e.g.,corresponding to a base station sector and tone block may be the same ordifferent with respect to another base station sector and tone block. Insome embodiments, at some times the superslot boundaries of differentlinks corresponding to connections with the same wireless terminal areoffset from one another. For example each sector at the base station mayuse the same basic downlink timing structure, but there may be an offsetfrom one base station sector with respect to an adjacent base stationsector, such that the superslot boundaries for the two links are offsetwith respect to one another.

Switching protocol information 248 includes information used toimplement the parameter switching rules regarding the change of aparameter, e.g., an encryption key, a scrambling mask identifier, arequest dictionary indicator. For example, a parameter switching messageindicates times for switching a parameter such as an encryption key withrespect to different links, each parameter switching point beingidentified as a superslot boundary in the timing structure of that link.However, some traffic channel segments assigned to the wireless terminalmay straddle the identified superslot boundary. Exemplary switchingprotocol information controls whether the particular segment is to beencoded using the old key or the new key. In some embodiments, differentrules apply for uplink and downlink traffic channel segments.

Wireless terminal data/information 244 includes a plurality of sets ofwireless terminal data/information (wireless terminal 1 data/information260, . . . , wireless terminal N data/information 262), each set ofinformation corresponding to a wireless terminal using base station 200as a point of attachment. WT 1 data/information 260 includes parameterswitching point message information 264, one or more sets of linkinformation (link 1 information 266, . . . , link N information 268),encryption keys (key 1 info 284, . . . , key M info 286), scramblingmasks 272 (scrambling mask 1 288, . . . , scrambling mask M 290), andrequest dictionary indicators 274 (indicator 1 information 292,indicator K information 294). Parameter switching point messageinformation 264 includes timing information 276 and, in someembodiments, link identifier information 282. Timing information 276,which defines a point in a timing structure includes a superslotidentifier 278 and a symbol time identifier 280. In some embodiments,within each ultraslot in a recurring timing structure there are 144indexed superslots, and within each superslot there are 114 indexed OFDMsymbol transmission time periods. Link identifier information 282, e.g.,a connection identifier, identifies the connection to which the timinginformation 276 corresponds.

Link 1 information 266 includes information corresponding to aconnection with WT 1, e.g., connection identification informationassociating the wireless communications link with a base stationattachment point, base station assigned wireless terminal identifier(s)associated with the link, air link resources allocated to that wirelesscommunications link such as downlink and uplink traffic channelsegments, user data to be communicated over that wireless communicationslink, information identifying parameters, e.g., keys, masks,dictionaries, to be used for communications over the link, and/orinformation indicating parameter switching points for the wirelesscommunications link.

Link N information 268 includes similar information to link 1information 266, but pertaining to link N.

FIG. 3 is a drawing of an exemplary wireless terminal 300, e.g., mobilenode, implemented in accordance with the present invention and usingmethods of the present invention. Exemplary wireless terminal 300 may beany of the wireless terminals (136,138, 144, 146, 152, 154, 168, 170,172, 174, 176, 178) of FIG. 1, mobile nodes (MN) 418 of FIG. 4 or MN 718of FIG. 7. Exemplary wireless terminal 300 includes a receiver module302, a transmitter module 304, a processor 306, user 110 devices 308,and memory 310 coupled together via a bus 312 over which the variouselements interchange data and information.

Receiver module 302, e.g., an OFDM receiver, is coupled to receiveantenna 303 via which the wireless terminal receives downlink signalsfrom base stations. Parameter switching point information is receivedvia receiver module 302. The wireless terminal 300 is capable ofmaintaining simultaneous wireless links with a plurality of base stationattachments points. Receiver module 302 includes a plurality ofconnection modules (connection 1 module 314, . . . , connection N module316), each connection module can be used for operation pertaining to adifferent simultaneous downlink link.

In some embodiments, each connection module (314, 316) includes apassband receiver chain tuned to receive the downlink tone block beingused by the corresponding attachment point for that link. In someembodiments, a separate antenna is used corresponding to each connectionmodule (314, 316). Receiver 302 also includes decoder module 318 whichdecodes at least some of the received downlink signals.

Transmitter module 304, e.g., an OFDM transmitter, is coupled totransmit antenna 305 via, which the wireless terminal 300 transmitsuplink signals to base stations. The wireless terminal 300 is capable ofmaintaining simultaneous wireless links with a plurality of base stationattachments points. Transmitter module 304 includes a plurality ofconnection modules (connection 1 module 315, . . . , connection N module317), each connection module can be used for operations pertaining to adifferent simultaneous uplink link. In some embodiments, each connectionmodule (315, 317) includes a passband transmitter chain tuned totransmit into the uplink tone block being used by the correspondingattachment point for that link. In some embodiments, a separate antennais used corresponding to each connection module (315, 317). In someembodiments, receiver connection 1 module 314 is paired with transmitterconnection 1 module 315, while receiver connection N module 316 ispaired with transmitter connection N module 317. The operation betweensuch a pair of modules is, in some embodiments, coordinated such as toadjust wireless terminal uplink timing to synchronize the wirelessterminal transmit signals' receive time at the base station attachmentpoint receiver with respect to the receive time of other wirelessterminals' transmit signals at the base station attachment point, e.g.,using closed loop timing control methods. Received base station downlinksignals from the base station attachment point and received timingadjustment feedback signals are used by the wireless terminal. In someembodiments, the same antenna or antennas are used for both the receivermodule 302 and transmitter module 304. Transmitter module 304 alsoincludes an encoder module 320 which encodes at least some of thedata/information to be communicated using the uplink.

User I/O devices 308, e.g., microphone, keyboard, keypad, camera,switches, speaker, display, etc., provide a user interface allowing theuser to input data/information, output data/information, and controloperations of the wireless terminal, e.g., initiate a communicationssession.

Memory 310 includes routines 322 and data/information 324. The processor306, e.g., a CPU, executes the routines 322 and uses thedata/information 324 in memory 310 to control the operation of thewireless terminal 300 and implement methods of the present invention.Routines 322 include a communications routine 326 and wireless terminalcontrol routines 328. The communications routine 326 implements thevarious communications protocols used by the wireless terminal 300. Thewireless terminal control routines 328 include a reference pointdetermination module 330, a switching point determination module 332, alink timing module 334, and a link determination module 336.

Reference point determination module 330 determines from receivedparameter switching point information, a reference point in timecorresponding to a first one of a plurality of wireless communicationslinks between the wireless terminal and base station attachment points.

The switching point determination module 332 determines individualparameter switching points from the determined reference point, eachdetermined individual parameter switching point corresponding to adifferent one of a plurality of wireless terminal 300 wirelesscommunications links. In some embodiments the switching pointdetermination module 332 determines individual parameter switchingpoints based on a predetermined relationship between the determinedreference point and potential parameter switching points for thecorresponding one of the wireless terminal 300 wireless communicationslinks. In some embodiments, the switching point determination module 332selects in a predetermined manner, a potential parameter switching pointcorresponding to the one of the plurality of wireless communicationslinks for which the individual parameter switching point is beingdetermined. For example, in some embodiments, potential parameterswitching points occur on superslot boundaries, and the superslotboundaries are identified from the recurring timing structurecorresponding to the link. For example, for each link the switchingpoint determination module 322 in some embodiments, selects the lastpreceding superslot boundary for the communications link which precedesthe determined reference point. In some other embodiments, for each linkthe switching point determination module 322, selects the nextsubsequent superslot boundary for the communications link with respectto the determined reference point.

Link timing module 334 maintains timing synchronization on a per linkbasis.

For example, a wireless terminal may have two concurrent links withdifferent base station attachment points, e.g., corresponding todifferent sectors of the same base station or corresponding to differentbase stations. The two attachment points are, in some embodiments, nottiming synchronized. In addition a link with respect to one attachmentpoint may have a different signal round trip time than another wirelesslink with respect to a different attachment point. Maintaining timingsynchronization at the base station attachment point with respect toeach uplink corresponding to the attachment point is important in anOFDM multiple access wireless communications system such as to limitinterference levels and closed loop timing control is implemented.

Link determination module 336 determines which one of a plurality oflinks is the first link to which the communicated switching point offsetapplies and is being referenced. In some embodiments, the linkdetermination module 336 determines which link is the first link frominformation included in the received parameter switching information,e.g., link identifier information such as a connection identifier fieldin a message, the connection identifier field including a cellidentifier, a sector type identifier, and a tone block identifier. Inother embodiments, the link determination module 336 determines whichlink is the first link by identifying which link the information wasreceived over, e.g., the link via which the parameter switchinginformation is communicated is the first link.

Data/information 324 includes user/device/session/resource information338, system data/information 340, received parameter switching pointinformation 358, determined reference point information 368, a pluralityof sets of determined link switch point information (determined link 1switch point information 370, . . . , determined link N switch pointinformation 372), encryption keys 374 (key 1 information 380, . . . ,key M information 382), scrambling masks 376 (scrambling mask 1information 384, . . . , scrambling mask M information 386), and requestdictionary indicators (request dictionary indicator 1 information 388, .. . , request dictionary indicator K information 390).

System data/information 340 includes a plurality of set of base stationdata information (base station 1 data/information 342, . . . , basestation n data 344) and switching protocol information 346. Base station1 data/information 348 includes a plurality of set of attachment pointinformation (attachment point 1 information 348, . . . , attachmentpoint N information 350). Attachment point 1 information 348 includesidentification information 352 and timing/frequency structureinformation 354. Timing/frequency structure information 354 includessuperslot boundary information 356.

Received parameter switching point information 358 includes timinginformation 360 and, in some embodiments, link identifier information366. Timing information 360 includes a superslot identifier 362 and asymbol time identifier 364. Determined link reference point information368 is an output of the reference point determination module 330.Determined link 1 switch point information 1 370 and determined link Nswitch point information 372 are outputs of the switching pointdetermination module 332. An encryption key is an exemplary parameterwhich is switched in response to a received switching point informationin accordance with the determined switching point corresponding to aparticular link and in accordance with the switching protocolinformation 340. Other exemplary parameters are scrambling masks, e.g.,used for scrambling the phase of an OFDM symbol, and request dictionaryindicators, e.g., used to indicate different request dictionaries eachrequest dictionary corresponding to a particular interpretation of anuplink traffic resource request report. In some embodiments, theparameter applies to both the uplink and the downlink, e.g., the sameencryption key in some embodiments is used for both uplink and downlinktraffic channel segments. In some such embodiments, the switching pointinformation is applied in relation to both the downlink and uplinktiming structures.

Various elements in the data/information 324 in WT 300 correspond tosimilarly named elements in the data/information 228 in BS 200, whichhave been previously described, and such descriptions are also relevantto WT 300.

FIG. 4 is a drawing 400 of a portion of an exemplary wirelesscommunications system implemented in accordance with the presentinvention and using methods of the present invention. The exemplarysystem of drawing 400 includes a base station (BS) 402 having a wirelesscoverage area represented by cell 1 404. BS 402 includes a plurality ofbase station sectors (base station sector 1 412, base station sector 2414, base station sector 3 416) each corresponding to a sector coveragearea (sector 1 406, sector 2 408, sector 3 410), respectively. Theexemplary system of drawing 400 also includes an exemplary wirelessterminal, mobile node (MN) 418. MN 418 is currently connected to a basestation sector 1 (BSS1) 412 attachment point as indicated by firstwireless communications link 420 and is currently connected to a basestation sector 2 (BSS 2) 15 414) attachment point as indicated by secondwireless communications link 422.

Multiple wireless communications links with the same base station sectorare also possible. For example, a first wireless communications link cancorrespond to a first tone block being used by the base station sectorand a second wireless communications link can correspond to a differenttone block being used by the same base station sector. In someembodiments, a tone block includes a set of contiguous OFDM tones, theset including at least 100 tones, e.g., 113 tones. In some embodiments,each base station sector supports up to three different downlink toneblocks.

FIG. 5 is a drawing 500 illustrating exemplary parameter switching inaccordance with the present invention. Block 502 illustrates anexemplary parameter switching message. The exemplary parameter switchingmessage 502 includes a connection identifier field 504, a superslotidentifier field 506 and a symbol time identifier field 508. In thisexample, the connection identifier field 504 indicates that secondconnection is the connection to which the time offset information offield 506 and field 508 apply. The superslot identifier field 506indicates superslot with index=4; the symbol time identifier field 508indicates that the OFDM symbol time index within the superslot is 57.Row 510 illustrates exemplary downlink timing in a repetitive timingstructure corresponding to a first connection, e.g., corresponding towireless communications link 420 in FIG. 4 between BSS1 412 and MN 418.Row 512 illustrates exemplary downlink timing in a repetitive timingstructure corresponding to a second connection, e.g., corresponding towireless communications link 422 in FIG. 4 between BSS2 414 and MN 418.Each superslot, in some embodiments, represents a time duration of afixed number of OFDM symbol transmission time periods, e.g., 114 OFDMsymbol transmission time periods.

Dotted line 514 indicates that the timing representing the start of asuperslot is slightly different corresponding to the two simultaneousconnections. In addition, in this example, the superslot indexing isoffset between the two connections.

In this example, the base station indicates a selected point in time 516with respect to the second connection via field 504 of message 502.Field 506 of message 502 identifies second connection superslot index=4as the superslot within the timing structure corresponding to the secondconnection in which the selected point in time 516 occurs. Field 508 ofmessage 502 indicates that the time offset A 520, from the start of 20superslot index=4 corresponding to the second connection to the selectedpoint in time 516 is 57 OFDM symbol time periods. Time offset B 522,from the start of the superslot index=3 corresponding to the firstconnection to the selected point in time 516 is 56.5 OFDM symbol timeperiods.

Although the value of 522 has not been directly communicated from thebase station to the wireless terminal via message 502, there is noambiguity as to when the parameter switching occurs with respect to the1st connection. The wireless terminal determines a selected point intime 516 with respect to the one connection identified in message 502.For each of the connections, the parameter switching point is thepreceding parameter switching boundary. In this case, the parameterswitching boundary is the start of a superslot. The base station hasintentionally chosen the selected point in time such that there will beno ambiguity as to which boundary each connection should use for theparameter switching point. In some embodiments, for each of thecommunications links, the selected point in time is offset from each ofthe intended switching points by at least one OFDM symbol time duration.In some embodiments, the selected point in time is chosen such that thetime interval between the selected point in time and the closestpotential switching point boundary is maximized or nearly maximized. Forexample, in this case of FIG. 5, the timing of the two connections isnearly identical with respect to the start of a superslot, and theselected point in time is chosen to be the center point of a superslotcorresponding to the 2nd connection.

Block 524 indicates 1st connection potential candidate parameterswitching points indicated by Os which occur at superslot boundariescorresponding to 1st connection timing. Block 524 also indicates thatthe first connection parameter switching point occurs at the start ofsuperslot with index=3 in the first connection timing, as indicated byan X, time 526.

Block 528 indicates 2nd connection potential candidate parameterswitching points indicated by Os which occur at superslot boundariescorresponding to 2nd connection timing. Block 528 also indicates thatthe second connection parameter switching point occurs at the start ofsuperslot with index=4 in the second connection timing, as indicated byan X, time 530. It should be noted that time 530 occurs slightly beforetime 526; however, there is no ambiguity between the base stationsectors and the wireless terminal as to which parameter is used at whattime with respect to the different simultaneous links.

FIG. 6 is a drawing 600 illustrating exemplary parameter switching inaccordance with the present invention. Block 602 illustrates anexemplary parameter switching message. The exemplary parameter switchingmessage 604 includes a connection identifier field 604, a superslotidentifier field 606 and a symbol time identifier field 608. In thisexample, the connector identifier field 604 indicates that the firstconnection is the connection to which the time offset information offields 606 and field 608 apply. The superslot identifier field 606indicates superslot with index=9; the symbol time identifier fieldindicates that the OFDM symbol time index within the superslot is 74.Row 610 illustrates exemplary downlink timing in a repetitive timingstructure corresponding to a first connection, e.g., corresponding towireless communications link 420 in FIG. 4 between BSSI 412 and MN 418.Row 612 illustrates exemplary downlink timing in a repetitive timingstructure corresponding to a second connection, e.g., corresponding towireless communications link 422 in FIG. 4 between BSS2 414 and MN 418.Each superslot, in some embodiments, represents a time duration of afixed number of OFDM symbol transmission time periods, e.g., 114 OFDMsymbol transmission time periods.

Dotted line 614 indicates that the timing representing the start of asuperslot is substantially different corresponding to the twosimultaneous connections. In addition, in this example, the superslotindexing is offset between the two connections.

In this example, the base station indicates a selected point in time 616with respect to the first connection via field 604 of message 602. Field606 of message 602 identifies first connection superslot index=9 as thesuperslot within the timing structure corresponding to the firstconnection in which the selected point in time 616 occurs. Field 608 ofmessage 602 indicates that the time offset A 620, from the start ofsuperslot index=9 corresponding to the first connection to the selectedpoint in time 616 is 74 OFDM symbol time periods. Time offset B 622,from the start of the superslot index=3 corresponding to the secondconnection to the selected point in time 616 is 40 OFDM symbol timeperiods.

Although the value of time offset B 622 has not been directlycommunicated from the base station to the wireless terminal via message602, there is no ambiguity as to when the parameter switching occurswith respect to the 2nd connection. The wireless terminal determines aselected point in time 616 with respect to the one connection identifiedin message 602. For each of the connections, the parameter switchingpoint is the preceding parameter switching boundary. In this case, theparameter switching boundary is the start of a superslot. The basestation has intentionally chosen the selected point in time such thatthere will be no ambiguity as to which boundary each connection shoulduse for the parameter switching point. In some embodiments, for each ofthe communications links, the selected point in time is offset from eachof the intended switching points by at least one OFDM symbol timeduration. In some embodiments, the selected point in time is chosen suchthat the time interval between the selected point in time and theclosest potential switching point boundary is maximized or nearlymaximized.

Block 624 indicates 1st connection potential candidate parameterswitching points indicated by Os which occur at superslot boundariescorresponding to 1st connection timing. Block 624 also indicates thatthe first connection parameter switching point occurs at the start ofsuperslot with index=9 in the first connection timing, as indicated byan X, time 626.

Block 628 indicates 2nd connection potential candidate parameterswitching points indicated by Os which occur at superslot boundariescorresponding to 2nd connection timing. Block 628 also indicates thatthe second connection parameter switching point occurs at the start ofsuperslot with index=3 in the second connection timing, as indicated byan X, time 630.

FIG. 7 is a drawing of an exemplary wireless communications system 700implemented in accordance with the present invention and using methodsof the present invention. The exemplary system 700 includes a first basestation (BS 1) 702 having a wireless coverage area represented by cell 1704. BS 702 includes a plurality of base station sectors (base stationsector 1 712, base station sector 2 714, base station sector 3 716) eachcorresponding to a sector coverage area (sector 1 706, sector 2 708,sector 3 710), respectively. The exemplary system 700 also includes anexemplary wireless terminal, mobile node (MN) 718. MN 718 is currentlyconnected to a base station sector 1 (BSS1) 712 attachment point asindicated by first wireless communications link 720 and is currentlyconnected to a base station sector 2 (BSS 2) 714 attachment point asindicated by second wireless communications link 722.

Exemplary wireless communications system 700 also includes a second basestation, BS 2 724 having a wireless coverage area represented by cell 2726. For example, base station 724 represents a single base stationsector which is used throughout the entire cell 726. Mobile Node 718 isalso currently connected to a BS 2 attachment point as indicated bythird wireless communications link 728.

BS 1 702 and BS 2 724 are coupled to network node 730, e.g., a router, acontrol node, etc, via network links (732, 734), respectively. Networknode 730 is also coupled to other network nodes, e.g., other basestations, routers, AAA nodes, home agent nodes, etc., via network link736. Network links (732, 734, 736) are, e.g., fiber optic links.

In some embodiments, the base stations (704, 706) may have differentnumbers of base station sectors, e.g., two, four, or more than foursectors. In some embodiments, at least some of the base station sectorssupport a plurality of different tone blocks, e.g., three differentdownlink tones blocks, each of the different downlink tone blockassociated with a corresponding different uplink tone block. Forexample, BSSI 712 may support three different downlink tone blocksand/or carriers, and each downlink tone block may correspond to adifferent potential BSS 1 attachment point. In such an exemplaryembodiment, a wireless terminal may have multiple simultaneousconnections with the same base station sector but use different toneblocks corresponding to each connection. In some embodiments, multiplebase stations are co-located at a site. For example, a first basestation using a first downlink carrier may be co-located with a secondbase station using a second downlink carrier, the second downlinkcarrier being different that the first downlink carrier.

FIG. 8 is a drawing 800 illustrating exemplary parameter switching inaccordance with the present invention. Block 802 illustrates anexemplary parameter switching message. The exemplary parameter switchingmessage 804 includes a connection identifier field 804, a superslotidentifier field 806 and a symbol time identifier field 808. In thisexample, the connector identifier field 804 indicates that the firstconnection is the connection to which the time offset information offields 806 and field 808 apply. The superslot identifier field 806indicates superslot with index=3; the symbol time identifier field 808indicates that the OFDM symbol time index within the superslot is 28.Row 810 illustrates exemplary downlink timing in a repetitive timingstructure corresponding to a first connection, e.g., corresponding towireless communication link 720 in FIG. 7 between BSSI 712 and MN 718.Row 810 illustrates exemplary downlink timing in a repetitive timingstructure corresponding to a second connection, e.g., corresponding towireless communications link 722 in FIG. 7 between BSS2 714 and MN 718.Row 814 illustrates exemplary downlink timing in a repetitive timingstructure corresponding to a third connection, e.g., corresponding towireless communications link 728 in FIG. 7 between BS 2724 and MN 718.Each superslot, in some embodiments, represents a time duration of afixed number of OFDM symbol transmission time periods, e.g., 114 OFDMsymbol transmission time periods.

Dotted line 816 indicates that the timing representing the start of asuperslot is slightly different corresponding to simultaneousconnections 1 and 2 and substantially different corresponding to the twosimultaneous connections 1 and 3. In addition, in this example, thesuperslot indexing is offset between the first and third connections.

In this example, the base station indicated selected point in time 818corresponding to message 802 is with respect to the first connection viafield 804 of message 802. Field 806 of message 802 identifies firstconnection superslot index=3 as the superslot within the timingstructure corresponding to the first connection in which the selectedpoint in time 818 occurs. Field 808 of message 802 indicates that thetime offset A 822, from the start of superslot index=3 corresponding tothe first connection to the selected point in time 818 is 28 OFDM symboltime periods. Time offset B 824, from the start of the superslot index=3corresponding to the second connection to the selected point in time 818is 30 OFDM symbol time periods. Time offset C 826, from the start of thesuperslot index=8 corresponding to the third connection to the selectedpoint in time 818 is 86 OFDM symbol time periods.

Although the value of time offset B 824 and the value of time offset C826 have not been directly communicated from the base station to thewireless terminal via message 802, there is no ambiguity as to when theparameter switching occurs with respect to the 2nd connection or the 3rdconnection. The wireless terminal determines a selected point in time818 with respect to the one connection identified in message 802. Foreach of the connections, the parameter switching point is the precedingparameter switching boundary. In this case, the parameter switchingboundary is the start of a superslot. The base station has intentionallychosen the selected point in time 818 such that there will be noambiguity as to which boundary each connection should use for theparameter switching point. In some embodiments, for each of thecommunications links, the selected point in time is offset from each ofthe intended switching points by at least one OFDM symbol time duration.In some embodiments, the selected point in time is chosen such that thetime interval between the selected point in time and the closestpotential switching point boundary is maximized or nearly maximized.

Block 828 indicates 1st connection potential candidate parameterswitching points indicated by Os which occur at superslot boundariescorresponding to 1st connection timing. Block 828 also indicates thatthe first connection parameter switching point occurs at the start ofsuperslot with index=3 in the first connection timing, as indicated byan X, time 830.

Block 832 indicates 2nd connection potential candidate parameterswitching points indicated by Os which occur at superslot boundariescorresponding to 2nd connection timing. Block 832 also indicates thatthe 2nd connection parameter switching point occurs at the start ofsuperslot with index=3 in the second connection timing, as indicated byan X, time 834.

Block 836 indicates 3rd connection potential candidate parameterswitching points indicated by Os which occur at superslot boundariescorresponding to 3rd connection timing. Block 836 also indicates thatthe 3rd connection parameter switching point occurs at the start ofsuperslot with index=8 in the second connection timing, as indicated byan X, time 838.

FIG. 9 is a flowchart 900 of an exemplary method of operating a basestation in accordance with the present invention. Flowchart 900illustrates an exemplary method of operating a base station to indicateto a wireless terminal, a plurality of parameter switching points,different ones of said parameter switching points corresponding todifferent wireless communications links, each of said wirelesscommunications links having a repetitive timing structure, each of theindicated plurality of switching points corresponding to a positionwithin the repetitive timing structure of a corresponding one of thedifferent wireless communications links. In some embodiments, theplurality of communications links are downlink communications links andthe downlink timing structure is the same for each of the wirelesslinks. In some embodiments, the plurality of communications links areasynchronous communications links. In some embodiments, the plurality ofparameter switching points corresponding to different links representswitching points for the same parameter. Examples of parameterscorresponding to a switching point parameter include an encryption key,a request dictionary indicator and a scrambling mask. Operation of theexemplary method starts in step 902 and proceeds to step 904.

In step 904, the base station selects an offset point in time withrespect to a first link of said communications links which is offset intime from the parameter switching point corresponding to said first linkby a time offset. In some embodiments, the symbol time is a time periodused to transmit an OFDM symbol. In some embodiments, the parameterswitching points for said plurality of communications links are limitedto occur at pre-selected timing boundaries within the recurring timingstructures of said plurality of communications links. In some suchembodiments, the pre-selected timing boundaries occur at fixed timespacings. For example, in some embodiments the pre-selected timingboundaries are superslot boundaries which are spaced apart by at least101 OFDM symbol transmission time periods, e.g., 114 OFDM symboltransmission time periods. In various embodiments, the pre-selectedtiming boundaries for each of the wireless links are offset from oneanother, e.g., the superslot boundaries of different communicationslinks are offset from one another. In some embodiments, each switchingpoint corresponding to each of said different communications links has apredetermined relationship to the selected offset point in time. Forexample, the predetermined relationship is that, for each of saiddifferent communications links the switching point for that wirelesseslink is a potential switching point for that wireless link immediatelypreceding the selected offset point in time, e.g., a superslot boundary,immediately preceding the selected offset point in time.

Step 904 includes sub-step 906. In sub-step 906, the base stationselects a time which occurs in the timing structure of said first linkwhich is offset from the parameter switching point corresponding to thefirst one link by at least one symbol time period and wherein theswitching point in time for each of the additional wirelesscommunications links in said plurality of different wirelesscommunications links are also offset from the selected offset point intime by at least one symbol time period. Operation proceeds from step904 to step 908.

In step 908, the base station transmits parameter switching informationto the wireless terminal. Step 908 includes sub-step 910. In sub-step910, the base station transmits information indicating said offset pointin time to the wireless terminal. For example, in some embodiments, thebase station transmits a superslot identifier, and a symbol timeidentifier. In some embodiments, the transmitting of sub-step 910 isperformed at a point in time, prior to said selected offset point intime, which precedes said switching point corresponding to the first onelink by at least 5 times the period between potential switching pointsin the repetitive timing structure of the first link. In some suchembodiments, the transmitting of step 910 is performed at a point intime, prior to said selected offset point in time, that precedes each ofsaid switching points corresponding to different ones of said differentcommunications links by at least 5 times the period between potentialswitching points in the repetitive timing structure being used for thelink corresponding to particular repetitive timing structure. In someembodiments, the generated switching point information which istransmitted corresponds to a switching point time for the first link atleast 40 superslots into the future. In some such embodiments, e.g.,wherein there are 144 superslots in an ultraslot, the generatedswitching point information which is transmitted corresponds to aswitching point time for the first link at most 143 superslots into thefuture.

In some embodiments, transmitting information indicating said offsetpoint in time includes transmitting said information indicating saidoffset point in time over the first link to which said offset point intime corresponds without transmitting express information identifyingwhich one of said plurality of links said offset point in timecorresponds to, e.g., sub-step 912 is not performed.

In some other embodiments, step 908 includes sub-step 912. In sub-step912, the base station transmits information indicating which one of saidcommunications links said offset point in time corresponds to. Forexample, the base station transmits a connection identifier. In variousembodiments, sub-step 910 and sub-step 912 are transmitted as part ofthe same message, e.g., a message including a connection identifier, asuperslot identifier, and a symbol time identifier.

FIG. 10 is a flowchart 1000 of an exemplary method of operating awireless terminal to receive and process parameter switching pointinformation in accordance with the present invention. Operation startsin step 1002, where the wireless terminal is powered on and initialized.Operation proceeds from start step 1002 to step 1004. In step 1004, thewireless terminal receives parameter switching point information over atleast one of a plurality of wireless communications links correspondingto the wireless terminal, said switching point information indicating apoint offset from a switching point. Step 1004 includes sub-step 1006.In sub-step 1006, the wireless terminal receives timing information,e.g., a superslot identifier and a symbol time identifier, referencedwith respect to a first wireless communication link, said first wirelesscommunications link being one of said plurality of wirelesscommunications links. In some embodiments, step 1004 includes sub-step1008. In sub-step 1008, the wireless terminal receives informationidentifying which communication link is the first wireless communicationlink. For example, a connection identifier is, in some embodiments,communicated to the wireless terminal along with the timing information.

In some embodiment, e.g., embodiments, where sub-step 1008 is notincluded, operation proceeds from step 1004 to step 1010. In otherembodiments, where sub-step 1008 is performed and step 1010 is notperformed, operation proceeds from step 1004 to step 1012.

In step 1010, the wireless terminal determines which communications linkis the first wireless communications link based on the communicationslink over which the parameter switching point information wascommunicated. For example, in some embodiments, the communications linkover which the parameter switching point information is communicated isthe first communications link. Operation proceeds from step 1010 to step1012.

In step 1012, the wireless terminal determines a reference point in timefrom the received parameter switching point information corresponding tothe first communications link. Operation proceeds from step 1012 to step1014.

In step 1014, the wireless terminal determines individual parameterswitching points, each determined individual parameter switching pointcorresponding to a different one of said plurality of wirelesscommunications links. Step 1014 includes sub-step 1014, which isperformed for each of the plurality of wireless communications links. Insub-step 1016, the wireless terminal determines an individual parameterswitching point based on a predetermined reference between thedetermined reference point and potential switching points, e.g.,superslot boundaries, for the corresponding one of the plurality ofwireless communications links. Sub-step 1016 includes sub-step 1018. Insub-step 1018, the wireless terminal selects the last precedingpotential parameter switching point corresponding to the one of saidplurality of wireless communications links for which the individualparameter switching point is being determined. Operation proceeds fromstep 1014 to step 1020.

In step 1020, the wireless terminal switches from an old parameter to anew parameter with respect to a plurality of wireless communicationslinks, said switching occurring on a link by link basis using thedetermined switching point corresponding to the link and storedswitching protocol information. For example, consider that potentialparameter switching points occur on superslot boundaries, and that thetiming structure with respect to superslot boundaries on each of theplurality of links is offset from one another, the determined parameterswitching points will be offset from one another. In addition considerthat the parameter which is to be switched from an old to new parameteris an encryption key, and that the stored switching protocol informationcalls for a coded traffic channel segment to be coded using a singleencryption key. Consider the following exemplary switching protocolrules which are used in some embodiments. For a given link, if thesegment is downlink segment which ends before or at the parameterswitching point the old key is used for the segment; if a segment is adownlink segment which ends after the parameter switching point the newkey is used. For the given link, if the segment is uplink segment whichstarts before the switching point the old key is used for the segment;if a segment is a uplink segment which starts on or after the parameterswitching point the new key is used.

An exemplary embodiment of the present invention will now be described.This section addresses issues relating to wireless terminal-base station(WT-BS) synchronization involving activation of a new cipher keyfollowing or as part of completion of a Security Association Protocol(SAP) exchange. This processing applies, in some embodiments, towhenever a SAP phase is undertaken, whether on power-up or handoff.

In the exemplary embodiment, the last message of the SAP exchange is aSAP.SecurityConfirm message, which the BS sends to the WT. This messageincludes a field “KeySyncInfo”, which carries the information to be usedas a reference for changing over to the newly negotiated cipher and/orauthentication key called “AirlinkCipherKey” and “AirlinkIntegrityKey”,respectively. In some embodiments, the AirlinkIntegrityKey is not usedand may be omitted. The description below refers to the use of theAirlinkCipherKey.

A WT may transmit and/or receive data over one or more wireless airlinkconnections that are part of the same link, e.g., a link layer link. Thesame AirlinkCipherKey is used for data protection over each of theconnections of the same link, except for a short time interval while theencryption key is being switched, during which both the old key and thenew key may be in use simultaneously. Encryption/decryption is appliedto each traffic channel segment of each connection independently. Eachsegment can be identified in time by a superslot index which can beimplemented using a wrap-around counter. Thus, the superslot index is avalue which wraps around after a predetermined number of time slots. Inthis exemplary embodiment, a superslot is a timing structure in arecurring timing structure that is being used for a connection, In oneembodiment a superslot includes a fixed number, e.g., 114, contiguousindexed OFDM symbol transmission time periods, e.g., with the indexnumber ranging from 0 to 113. In some embodiments superslots are indexedin a larger grouping of OFDM symbol transmission time periods. Forexample in one exemplary embodiment, the larger grouping is anultraslot, said ultraslot including a fixed number of indexedsuperslots, e.g., 144 indexed superslots, e.g., with the index valueranging from 0 to 143. The indexing of the superslots repeats from oneultraslot to the next ultraslot.

Consider one of the connections. The encryption/decryption key willchange at the beginning of a “key-change” superslot. To each trafficchannel segment, the keychange superslot is assigned as follows. To eachuplink traffic channel segment, the keychange superslot is assigned tobe the one at which the segment starts. To each downlink traffic channelsegment, the key-change superslot is the one at which the segment ends.Which key is used for encryption/decryption of a traffic channel segmentwill depend on the superslot assigned to that segment. Thus, for eachconnection, the information used to identify when the new key is to beapplied includes a superslot index, say “X”. If a traffic channelsegment has an assigned superslot which is before the next superslotwith index “X” after SAP.SecurityConfirm message was received, the oldkey is used to encrypt/decrypt that segment. If a traffic channelsegment has an assigned superslot which is the next superslot with index“X” after SAP.SecurityConfirm message was received or a later superslot,the new key is used to encrypt/decrypt that segment. The computation ofthe superslot index “X” for each connection from the KeySyncInfo fieldis addressed below.

The KeySyncInfo field is 4-byte long and is composed of the followingvalues (connection ID value, superslot counter (ctr) value, symbolcounter value), which are concatenated in the order shown and describedbelow.

KeySyncInfo format Body

The KeySyncInfo field includes a two byte connection identification (Cm)field followed by a 1 byte Superslot counter field followed by a 1 byteSymbol counter field. The two byte CID is the cm of the connection whichthe two counters following the cm refer to. The 1 byte superslot counteris the Superslot counter within ultraslot, i.e., the index of thesuperslot at the beginning of which the key change is to take place forthis connection. Sometimes this counter is referred to as“UltraslotSuperslotIndex”. The 1 byte symbol counter is the Symbolcounter within the superslot, i.e. the index of a symbol in thesuperslot, which allows computation of the superslot number when the keychange is to take place for each of the other connections under the samelink. Sometimes this counter is referred to as“SuperslotOFDMSymbolIndex”.

A value of 255 in both subfields “Superslot Ctr” and “Symbol Ctr” isused to indicate that the encryption key is to be switched by the WTimmediately upon receiving SAP.SecurityConfirm message. This setting isused when the SAP exchange is done as part of the network accessoperation, i.e. when the WT has no previous key with this BS.

The key-change superslot index “X” is computed in the exemplaryembodiment from the KeySyncInfo field as follows:

(1) For the connection with the CID conveyed in the first value field ofthe KeySynclnfo field (named “CO”), superslot “XO” is the superslotcounter (i.e. second value) in the KeySyncInfo field.(2) (2) For each additional connection “Ci”, if its symbol “Yi” ofsuperslot “Si” aligns15 in time with connection “CO”'s symbol 0 of superslot 0, thenXi=mod(XO+Si+floor<<YO+Yi)/SS_SYMBOLS), US_SUPERSLOTS), where “YO” is the symbol counter intheKeySyncInfo field, SS_SYMBOLS is the total number of symbols in asuperslot, andUS_SUPERSLOTS is the total number of superslots in an ultraslot. In someembodiments, SS_SYMBOLS=114 and US_SUPERSLOTS=144.

Note that, in some embodiments, there can be an ambiguity of 1 in thevalue of Yi in the second bullet above, as the symbols of the twoconnections may not exactly align. To deal with this case, the basestation chooses the symbol counter subfield so that the ambiguity isirrelevant, i.e. so that the same Xi results whether any of the possibleYi's is assumed by the WT. In addition, the base station generates theKeySyncInfo to correspond to a time at least a sufficient number ofsuperslots, e.g., 40 superslots, into the future to ensure that the WTwill successfully receive the SAP.SecurityConfirm message before thetime to switch the key has come. The base station generates aKeySyncInfo to correspond to a time at most US_SUPERSLOTS-1 into thefuture. For example the base station generates a KeySyncInfo tocorrespond to a time at most 143 superslots into the future in anexemplary embodiment where there are 144 superslots per ultraslot.

An example of computation of the superslot index “X” is described belowbelow. The 2 byte cm field includes an unsigned integer value which isassociated with connection 0, the superslot counter field includes anunsigned integer value=102, and the symbol counter field includes andunsigned integer value=21.

Assume that SS_SYMBOLS=114, US_SUPERSLOTS=144, and that anotherconnection C1 aligns with the named connection CO as follows: SymbolY1=99 of superslot S1=36 aligns with CO's symbol 0 of superslot O. Fromthe KeySyncInfo, XO=102 and YO=21. Then to compute the superslot X1,X1=mode 102+36+floor ((21+99)/114), 144)=139. Thus, for connection C1,the new key is applied starting with the next superslot number 139.

In accordance with the present invention, a base station generates theKeySyncInfo and communicates the information to the wireless terminal.The generation method including selecting a symbol counter value suchthat there will be no ambiguity at the wireless terminal when decidingwhere new key application occurs with respect to each of the one or moreconnections corresponding to the same link. The wireless terminalreceives and processes the communicated KeySyncInfo determining when thenew key is started with respect to each of the one or more connectionscorresponding to the same link.

The techniques of the present invention may be implemented usingsoftware, hardware and/or a combination of software and hardware. Thepresent invention is directed to apparatus, e.g., mobile nodes such asmobile terminals, base stations, communications system which implementthe present invention. It is also directed to methods, e.g., method ofcontrolling and/or operating mobile nodes, base stations and/orcommunications systems, e.g., hosts, in accordance with the presentinvention. The present invention is also directed to machine readablemedium, e.g., ROM, RAM, CDs, hard discs, etc., which include machinereadable instructions for controlling a machine to implement one or moresteps in accordance with the present invention.

In various embodiments nodes described herein are implemented using oneor more modules to perform the steps corresponding to one or moremethods of the present invention, for example, signal processing,message generation and/or transmission steps. Thus, in some embodimentsvarious features of the present invention are implemented using modules.Such modules may be implemented using software, hardware or acombination of software and hardware. Many of the above describedmethods or method steps can be implemented using machine executableinstructions, such as software, included in a machine readable mediumsuch as a memory device, e.g., RAM, floppy disk, etc. to control amachine, e.g., general purpose computer with or without additionalhardware, to implement all or portions of the above described methods,e.g., in one or more nodes. Accordingly, among other things, the presentinvention is directed to a machine-readable medium including machineexecutable instructions for causing a machine, e.g., processor andassociated hardware, to perform one or more of the steps of theabove-described methods).

While described in the context of an OFDM system, at least some of themethods and apparatus of the present invention, are applicable to a widerange of communications systems including many non-OFDM and/ornon-cellular systems.

Numerous additional variations on the methods and apparatus of thepresent invention described above will be apparent to those skilled inthe art in view of the above description of the invention. Suchvariations are to be considered within the scope of the invention. Themethods and apparatus of the present invention may be, and in variousembodiments are, used with CDMA, orthogonal frequency divisionmultiplexing (OFDM), and/or various other types of communicationstechniques which may be used to provide wireless communications linksbetween access nodes and mobile nodes. In some embodiments the accessnodes are implemented as base stations which establish communicationslinks with mobile nodes using OFDM and/or CDMA. In various embodimentsthe mobile nodes are implemented as notebook computers, personal dataassistants (PDAs), or other portable devices includingreceiver/transmitter circuits and logic and/or routines, forimplementing the methods of the present invention.

1. A wireless terminal, comprising: means for receiving parameterswitching point information over at least one of a plurality of wirelesscommunications links corresponding to the wireless terminal, saidswitching point information indicating a point offset from a switchingpoint; means for determining, from the received parameter switchingpoint information, a reference point in time corresponding to a firstone of said plurality of communications links; and means for determiningindividual parameter switching points from said determined referencepoint, each determined individual parameter switching pointcorresponding to a different one of said plurality of wirelesscommunications links.
 2. The wireless terminal of claim 1, wherein saidmeans for determining a reference point in time determines individualparameter switching points based on a predetermined relationship betweenthe determined reference point and potential parameter switching pointsfor the corresponding one of said plurality of wireless communicationslinks.
 3. The wireless terminal of claim 2, wherein said means fordetermining individual parameter switching points includes using afunction to determine said individual parameter switching points, saidfunction being implemented in accordance with said predeterminedrelationship and using modular arithmetic computation.
 4. The wirelessterminal of claim 2, further including: means for storing informationindicating potential parameter switching points in a recurringcommunication link timing structure, wherein said switching pointdetermination module selects, in a predetermined manner, a potentialparameter switching point corresponding to the one of said plurality ofwireless communications links for which an individual parameterswitching point is being determined.
 5. The wireless terminal of claim4, wherein potential parameter switching points are super slotboundaries and wherein the predetermined manner includes selecting thelast preceding superslot boundary occurring in the communications linkpreceding said reference point.
 6. A machine-readable medium havinginstructions for causing a machine to execute the following steps:receiving parameter switching point information over at least one of aplurality of wireless communications links corresponding to a wirelessterminal, said switching point information indicating a point offsetfrom a switching point; determining, from the received parameterswitching point information, a reference point in time corresponding toa first one of said plurality of communications links; and determiningindividual parameter switching points from said determined referencepoint, each determined individual parameter switching pointcorresponding to a different one of said plurality of wirelesscommunications links.
 7. The machine-readable medium of claim 6, whereinsaid step of determining a reference point in time includes determiningindividual parameter switching points based on a predeterminedrelationship between the determined reference point and potentialparameter switching points for the corresponding one of said pluralityof wireless communications links.
 8. The machine-readable medium ofclaim 7, wherein said step for determining individual parameterswitching points includes using a function to determine said individualparameter switching points, said function being implemented inaccordance with said predetermined relationship and using modulararithmetic computation.
 9. The machine-readable medium of claim 7,further including the step of: storing information indicating potentialparameter switching points in a recurring communication link timingstructure, wherein said switching point determination module selects, ina predetermined manner, a potential parameter switching pointcorresponding to the one of said plurality of wireless communicationslinks for which an individual parameter switching point is beingdetermined.
 10. The machine-readable medium of claim 9, whereinpotential parameter switching points are super slot boundaries andwherein the predetermined manner includes selecting the last precedingsuperslot boundary occurring in the communications link preceding saidreference point.
 11. A base station for use in a communications systemwherein a wireless terminal can have a plurality of communicationslinks, each of said wireless communications links having a repetitivetiming structure, the base station comprising: means for selecting anoffset point in time with respect to a first link in said plurality ofsaid communications links which is offset in time from a parameterswitching point corresponding to the first link by a time offset; saidtime offset being selected for use in indicating a plurality ofswitching points, each switching point corresponding to a positionwithin the repetitive timing structure of a corresponding one of thedifferent communication links; and means for transmitting informationindicating said offset point in time to the wireless terminal therebyindicating to the wireless terminal a plurality of parameter switchingpoints, different ones of said parameter switching points correspondingto different wireless communications links.
 12. The base station ofclaim 11, wherein said means for selecting selects an offset point intime with respect to a first link by selecting a time which occurs inthe timing structure of said first link which is offset from theparameter switching point corresponding to the first link by at leastone symbol time period.
 13. The base station of claim 12, wherein saidswitching point in time for each of the additional wirelesscommunications links in said plurality of different wirelesscommunications links are also offset from the selected offset point intime by at least one symbol time period.
 14. The base station of claim13, further comprising a transmission control means for controlling saidtransmitter module to transmit to the wireless terminal informationindicating which one of said communications links said offset point intime corresponds to.
 15. The base station of claim 13, wherein saidtransmission control means corresponds to the first communication linkand transmits said information indicating said offset point in time overthe first link to which said indicated offset point in time correspondswithout transmitting express information identifying which one of saidplurality of links said offset point in time corresponds to.
 16. Amachine-readable medium having instructions for causing a machine toexecute the following steps: selecting an offset point in time withrespect to a first link in said plurality of said communications linkswhich is offset in time from a parameter switching point correspondingto the first link by a time offset; said time offset being selected foruse in indicating a plurality of switching points, each switching pointcorresponding to a position within the repetitive timing structure of acorresponding one of the different communication links; and transmittinginformation indicating said offset point in time to the wirelessterminal thereby indicating to the wireless terminal a plurality ofparameter switching points, different ones of said parameter switchingpoints corresponding to different wireless communications links.
 17. Themachine-readable medium 16, wherein in said selecting step san offsetpoint in time with respect to a first link I determined by selecting atime which occurs in the timing structure of said first link which isoffset from the parameter switching point corresponding to the firstlink by at least one symbol time period.
 18. The machine-readable mediumof claim 17, wherein said switching point in time for each of theadditional wireless communications links in said plurality of differentwireless communications links are also offset from the selected offsetpoint in time by at least one symbol time period.
 19. Themachine-readable medium of claim 18, further comprising a transmissioncontrol means for controlling said transmitter module to transmit to thewireless terminal information indicating which one of saidcommunications links said offset point in time corresponds to.
 20. Themachine-readable medium of claim 18, wherein said transmission controlmeans corresponds to the first communication link and transmits saidinformation indicating said offset point in time over the first link towhich said indicated offset point in time corresponds withouttransmitting express information identifying which one of said pluralityof links said offset point in time corresponds to.